Antiknock motor fuel



Patented Feb.,20, 1934 PATENT OFFICE ANTIKNOCK MOTOR FUEL Ludwig Rosenstein, San Francisco, Calif., as-

slgnor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application January 21, 1930 Serial No. 422,286

9 Claims.

My invention relates to anti-knock compounds which are useful in connection with liquid fuels for internal combustion engines. It is well known that an effect may arise in internal combustion engines which is unfavorable to the most efficient operation of the engine. This effect is the phenomenon which is commonly termed knocking or pinking" and which is undesirable.

It is the broad object of my invention to provide compounds which may be employed with liquid fuels in internal combustion engines to subdue this undesirable knocking.

My invention possesses other advantageous features which will appear in the following specification. It is to be understood that the invention; as defined by the claims, is to be accorded a range of equivalents consistent with the state of the prior art.

The fuels useful in internal combustion engines each have a pressure, termed the critical compression pressure, above which the fuel, when compressed in an internal combustion engine cyllnder, detonates or pinks. I have discovered that organic compounds containing carbon and nitrogen combined as the nitrile or isonitrile group are suitable agents for addition to the .hydrocarbon fuel to prevent this knocking. I have found the organo-metallo-cyanides particularly useful as such agents. As examples of the organovmetallo-cyanides which I have prepared I'will mention the esters of metallo-cyanic acids, for example the tetra ethyl ester, the tetra isopropyl ester and the tetra amyl ester of hydro-ferro cyanic acid by which acid I refer to that having the formula H4Fe(CN)5. In addition to these, I have prepared and employed the salts of metallo-cyanic acids with organic bases such as aniline and other aromatic and aliphatic amines. Aryl as well as alkyl esters may be used, as for 4 example tetra phenyl ferrocyanide. As an example of an organic compound of the type mentioned above, but containing no metallic element,

I have prepared isobutyl isonitrile and have found some instances, the nitrogen and carbon may be combined as isocyanides". Accordingly, it is my intention that the term cyanide should embracethose compounds known as cyanides, isocyanides, cyanogen complexes and their equivalents, irrespective of whether or not the elements are in the relationship normal to the cyano 61) group.

From experiments which I have conducted it appears that the anti-knock properties of the compounds above mentioned are due to the cyano radical, and in part to the metallic elements 07, when such are present. The valencyof carbon in the free cyano radical is other than four; in the isonitriles and isocyanides themselves it is two. Anti-knock properties, to some extent, are to be found associated with compounds containing carbon with a valency other than four or capable of giving rise, under cylinder conditions, to compounds or free radicals containingcarbon with a valency other than four. This. is borne out by the behavior of cyanogen iodide which is 5;. an anti-knockof greater effect than attributable to the iodine in the compound.

While I have mentioned derivatives oi. ferrocyanides above, it is to be understood that I do not wish to limit my invention to such hexacys9 anic compounds, but wish to include also organic derivatives of the metallo-pentacyanides and compounds containing within the complex radical other groups as well as the cyanide; such compounds for example as the m'troprussides in 5 which one cyanide group is replaced by NO, or carbonyl cyanides in which some of the cyanide is replaced by CO,'are included as are organic derivatives of other complex cyanides and of metals other than iron. Also, while I have speg0 cifically mentioned the preparation of the organic derivatives of the ferrocyanides it is to be borne in mind that no limitation is to be imposed upon my invention by this fact since other metals may be employed to form metallo-cyanides of which 5 the esters may be prepared. In this connection for example, nickel, lead and osmium may be utilized. Tungsten which forms octa-oyano com plexes may also be utilized. The cyano compounds of certain non-metals as for instance, 10- dine, mentioned above, and selenium may also be used.

It is a desirable feature of an anti-knock compound that it be soluble in the hydrocarbon fuel with whichit is to be employed. This quality is to be found in many of the organo-metallic-cyw. nides, particularly the esters previously mentioned which are either directly soluble in the fuel orin mixtures thereof with other compounds such as alcohols, which serve as auxiliary solvents.

I have found that it is not necessary that the anti-knock agents of my invention are of nearly the same volatility as of the fuel; unvaporized particles will have the same effect. For example, the organo-metallo cyanides are non-volatile as compared to the volatility of the fuel. Many of the cyanides are solids at ordinary temperatures. It will be understood that the term "vo1atile is a relative term and that by nonvolatile compound I mean a compound the volatility of which is less than that of the least volatile constituent of the fuel.

In preparing hydrocarbon fuels in accordance with my invention I have dissolved about 0.2% to 0.4% of tetra-isopropyl ester of hydro-ferrocyanic acid in a cracked gasoline containing about 9% isopropyl alcohol or a small percentage of cyclo-hexanol. The alcohol serves to dissolve and to facilitate the incorporation of the ester of the hydro-ferrocyanic acid in the gasoline. Such mixtures are decided anti-knock fuels when employed in an engine. The ethyl ester of hydro-ferrocyanic acid was similarly employed with success. With the amyl ester but 2% of amyl alcohol was necessary to effect its incorporation in the gasoline in sufficient quantity to subdue the knocking materially. While it is well known that isopropyl alcohol and other alcohols possess anti-knock properties in themselves, the quantity of alcohol utilized in this instance is insuflicient to affect so markedly the original critical compression pressure of the hydrocarbon fuel.

When incorporating the tetra-isopropyl ester of hydro-ferrocyanic acid in a straight run gasoline but 5% of amyl alcohol is necessary to effect solution of sufficient ester to greatly reduce knocking. It appears that amyl alcohol is superior to the lower alcohols in this connection.

By the term "hydrocarbon fuel" as used in the claims I wish to include materials useful as fuels in internal combustion engines, as gasoline, kerosene, alcohol, benzene, and mixtures of any of these, etc.

I claim:

1. A motor fuel for internal combustion engines comprising a hydrocarbon fuel and an organic derivative of a metallo-cyano acid.

2. A motor fuel for internal combustion engines comprising a hydrocarbon fuel and an ester of a metallo-cyano acid.

3. A motor fuel for internal combustion engines comprising a hydrocarbon fuel and an organo -ferrocyano compound.

4. A motor fuel for internal combustion engines comprising a hydrocarbon fuel and an organo-metallo compound of the general formula RM:cYz(CN)6-z, wherein R represents an organic substituent, M represents a metallic element, Y represents a univalent radical and a: and 2 represent the combining values of the elements and radicals respectively.

5. A motor fuel for internal combustion engines comprising a hydrocarbon fuel and an organic salt of a metallo-cyano acid.

6. A hydrocarbon fuel for internal combustion engines comprising a salt of a metallo-cyano acid with an alkylamine.

'7. A motor fuel for internal combustion engines comprising a hydrocarbon fuel and a salt of a metallo-cyano acid with an arylamine.

- 8. A motor fuel for internal combustion engines comprising a hydrocarbon fuel and an alkyl LUDWIG ROSENSTEIN. 

